The first successful procedure for salvaging shed blood during an operation or emergency situation was used more than 150 years ago, in conjunction with reinfusion of blood to hemorrhaging women subsequent to child birth. This procedure, since termed autologous transfusion or autotransfusion, is now widely employed. The return of a patient's own blood is preferred to transfusion of blood from others because of biological compatibility. Autologous transfusion techniques include taking blood from a patient prior to surgery and returning it later during surgery as well as temporarily removing a quantity of whole blood and replacing it with isotonic solution. The latter procedure enables return of whole blood units to the patient after major surgery, with less cell damage from pumps artificial organ devices, such as an oxygenator, for example.
A number of systems have been developed over the last 20 years for use in autotransfusion applications. Some merely collect the blood, filter from it relatively large particle matter such as bone fragments from a traumatic incident, and return the blood under positive pressure to the patient. These systems are of limited applicability because they can neither concentrate the blood cells nor remove free hemoglobin, activated clotting factors or small cell debris.
Other autotransfusion machines, such as the "Cell Saver" of Haemonetics Corporation of Braintree, Mass., use centrifugation to both wash and concentrate salvaged blood. This product uses a batch processing approach and employs an expensive disposable, and therefore has limited flexibility while being of substantial cost. However, the washing removes a number of constituent factors which can adversely affect the patient, such as liberated red cell enzymes, activated clotting factors and anticoagulant, and concentrates the cells, so a higher quality blood mass is returned to the patient. Although this type of device represents the current state of the art in autotransfusion technology, its use in surgical procedures is limited because a large minimum volume of packed red cells is required for this batch process. The same problems exist with a centrifugal unit offered by Cobe Laboratories of Lakewood, Colo., but developed originally by IBM, for washing shed surgical blood. This unit is less expensive than the Haemonetics "Cell Saver" but much slower and more awkward to use. Both systems employ a saline solution for washing. A wholly different approach for autotransfusion, which apparently does not employ cell washing, is disclosed in U.S. Pat. No. 4,501,581 to Kurtz et al. In this system, primary attention is focused on deaerating the blood drawn into a collection chamber before forcing it back into the patient's circulatory system.
It is evident, therefore, that there is a need for a system that can concentrate blood cells, particularly for autologous transfusion, while also eliminating or minimizing the presence of activated substances and intracellular debris in the concentrate. The overall objectives are to return a high hematocrit concentrate to the patient (or to storage for later reinfusion), while minimizing the presence of adverse factors such as activated substances, intracellular debris, solid molecular waste and surgical solutions (anticoagulants, salines, etc). The system should, moreover, be capable of functioning in a wide variety of applications ranging from elective surgery to emergency surgery. Thus the system should be capable of functioning with different flow rates, volumes and condition of blood, and should utilize low cost disposables. Specifically, any disposable should be configured to be easily insertable into and removable from a machine without allowing contamination from one patient to be transmitted to another. It should also be so inexpensive as to introduce only a relatively low added cost to the procedure. And finally, it should operate on a real time, on-line basis, with sufficient versatility of operation to meet different conditions that may be encountered, such as a need for immediate return of shed blood to the patient.
More recently, superior systems for plasmapheresis, or the extraction of plasma from whole blood, have been disclosed in the above-referenced related patent applications of Halbert Fischel entitled "BLOOD FRACTIONATION SYSTEM AND METHOD", filed Dec. 13, 1982, Ser. No. 449,470, and of Donald W. Schoendorfer entitled "METHOD AND APPARATUS FOR SEPARATION OF MATTER FROM SUSPENSION", filed Mar. 21, 1984, Ser. No. 591,925. As described therein, blood passed into a gap between a rotating spinner and a relatively fixed wall, under proper conditions of gap size, spinner diameter, rotational velocity, and flow rates is believed to generate controlled and enhanced Taylor vortices within the gap. Consequently, matter, such as plasma, in the blood that is sized small enough to pass through the pores of a membrane on either the spinner or the shell will pass through the membrane at rates substantially in excess of those heretofore achieved under similar shear and flow rate levels. Fischel describes a cell washing application where an isotonic washing solution is passed through a porous fixed outer wall of the filter into the gap area. Schoendorfer describes the admission of rinsing solutions into the gap area at or in conjunction with the point of blood admission to the gap. Furthermore, even though the action can be continuous or intermittent, surface clogging and deposition phenomena are far less significant than in planar membrane systems. Where flow throughputs drop, moreover, the dynamic fluid conditions can be changed so as to aid in clearing the membrane as filtration continues. Systems utilizing this technology, such a the "Autopheresis-C" system of HemaScience Laboratories, Inc., operate very sensitively but stably with safeguards against the many factors that can affect patient comfort and safety.